The Vacation Reply/Auto-Reply also works as a filter and works at position/priority 7. If an email is moved to a folder, or otherwise prevented from reaching filter position 7 then no auto-reply is sent.

Hi, I'm impressed by the Runbox website and it looks like you have a great email system.
My questions would not be in any way a deciding factor but I would like to ask about spam filtering for multiple users.
Could I create a Filter that applies to all email addresses for my domain name?
Or is it possible to create a Filter in one email account, export it and then import it in to each of the other email accounts?